This chapter discusses the history of Ashʿarism in the fourth to fifth/tenth to eleventh centuries. Ashʿarism was, besides Māturīdism, the most important school of Sunnikalām. After the decline of Muʿtazilism, it became the predominant theological school, primarily among the adherents of the Shāfiʿite and the Mālikite school of law. There is a wide scholarly consensus that Ashʿarism entered a new phase in the sixth/twelfth century, marked by an increasing influence of Avicennan philosophy, a transition generally associated with the prominent thinker Abū Ḥāmid al-Ghazālī. This chapter focuses on theologians that preceded this methodological shift. It first charts the rise of Ashʿarism, highlighting the contributions of three key figures to the elaboration and broader dissemination of the school’s teachings: Abū Bakr Ibn Fūrak, Abū Isḥāq al-Isfarāʾīnī, and Abū Bakr al-Bāqillānī. It concludes with an assessment of Ashʿarism under the patronage of Niẓām al-Mulk.